Nonlinear optics (NLO) is the branch of optics that describes the behaviour of light in nonlinear media, that is, media in which the polarization density P responds non-linearly to the electric field E of the light. The non-linearity is typically observed only at very high light intensities (when the electric field of the light is >108 V/m and thus comparable to the atomic electric field of ~1011 V/m) such as those provided by lasers. Above the Schwinger limit, the vacuum itself is expected to become nonlinear. In nonlinear optics, the superposition principle no longer holds.
An optical amplifier is a device that amplifies an optical signal directly, without the need to first convert it to an electrical signal. An optical amplifier may be thought of as a laser without an optical cavity, or one in which feedback from the cavity is suppressed. Optical amplifiers are important in optical communication and laser physics. They are used as optical repeaters in the long distance fiber-optic cables which carry much of the world's telecommunication links.
Titanium-sapphire lasers (also known as Ti:sapphire lasers, Ti:Al2O3 lasers or Ti:sapphs) are tunable lasers which emit red and near-infrared light in the range from 650 to 1100 nanometers. These lasers are mainly used in scientific research because of their tunability and their ability to generate ultrashort pulses thanks to its broad light emission spectrum. Lasers based on Ti:sapphire were first constructed and invented in June 1982 by Peter Moulton at the MIT Lincoln Laboratory.
In optics, the Pockels effect, or Pockels electro-optic effect, is a directionally-dependent linear variation in the refractive index of an optical medium that occurs in response to the application of an electric field. It is named after the German physicist Friedrich Carl Alwin Pockels, who studied the effect in 1893. The non-linear counterpart, the Kerr effect, causes changes in the refractive index at a rate proportional to the square of the applied electric field. In optical media, the Pockels effect causes changes in birefringence that vary in proportion to the strength of the applied electric field.
An optical parametric amplifier, abbreviated OPA, is a laser light source that emits light of variable wavelengths by an optical parametric amplification process. It is essentially the same as an optical parametric oscillator, but without the optical cavity.
In optics, an ultrashort pulse, also known as an ultrafast event, is an electromagnetic pulse whose time duration is of the order of a picosecond or less. Such pulses have a broadband optical spectrum, and can be created by mode-locked oscillators. Amplification of ultrashort pulses almost always requires the technique of chirped pulse amplification, in order to avoid damage to the gain medium of the amplifier.
An optical neural network is a physical implementation of an artificial neural network with optical components. Early optical neural networks used a photorefractive Volume hologram to interconnect arrays of input neurons to arrays of output with synaptic weights in proportion to the multiplexed hologram's strength. Volume holograms were further multiplexed using spectral hole burning to add one dimension of wavelength to space to achieve four dimensional interconnects of two dimensional arrays of neural inputs and outputs. This research led to extensive research on alternative methods using the strength of the optical interconnect for implementing neuronal communications.
Chirped pulse amplification (CPA) is a technique for amplifying an ultrashort laser pulse up to the petawatt level, with the laser pulse being stretched out temporally and spectrally, then amplified, and then compressed again. The stretching and compression uses devices that ensure that the different color components of the pulse travel different distances.
Raman amplification is based on the stimulated Raman scattering (SRS) phenomenon, when a lower frequency 'signal' photon induces the inelastic scattering of a higher-frequency 'pump' photon in an optical medium in the nonlinear regime. As a result of this, another 'signal' photon is produced, with the surplus energy resonantly passed to the vibrational states of the medium. This process, as with other stimulated emission processes, allows all-optical amplification. Optical fiber is today most used as the nonlinear medium for SRS for telecom purposes; in this case it is characterized by a resonance frequency downshift of ~11 THz. The SRS amplification process can be readily cascaded, thus accessing essentially any wavelength in the fiber low-loss guiding windows. In addition to applications in nonlinear and ultrafast optics, Raman amplification is used in optical telecommunications, allowing all-band wavelength coverage and in-line distributed signal amplification.
Injection seeders are devices that direct the output of small "seed" lasers into the cavity of a much larger laser to stabilize the latter's output. Most seed lasers are stable, single-frequency lasers that emit within the linewidth of the larger laser's gain medium. The single frequency encourages the larger laser to lase in a single longitudinal mode, and the seed laser can also improve the laser's spatial profile and improve the M2 parameter. Seed lasers can be continuous or pulsed. Seeding a pulsed laser can reduce variations in the output energy and timing (jitter) from pulse to pulse, and smooth out temporal variations within the pulse. Many commercial lasers use a laser diode as a seeding source.
In nonlinear optics, filament propagation is propagation of a beam of light through a medium without diffraction. This is possible because the Kerr effect causes an index of refraction change in the medium, resulting in self-focusing of the beam.
A fiber laser is a laser in which the active gain medium is an optical fiber doped with rare-earth elements such as erbium, ytterbium, neodymium, dysprosium, praseodymium, thulium and holmium. They are related to doped fiber amplifiers, which provide light amplification without lasing.
Silicon photonics is the study and application of photonic systems which use silicon as an optical medium. The silicon is usually patterned with sub-micrometre precision, into microphotonic components. These operate in the infrared, most commonly at the 1.55 micrometre wavelength used by most fiber optic telecommunication systems. The silicon typically lies on top of a layer of silica in what is known as silicon on insulator (SOI).
The Vulcan laser is an infrared, 8-beam, petawatt neodymium glass laser at the Rutherford Appleton Laboratory's Central Laser Facility in Oxfordshire, United Kingdom. It was the facility's first operational laser.
In optics, a supercontinuum is formed when a collection of nonlinear processes act together upon a pump beam in order to cause severe spectral broadening of the original pump beam, for example using a microstructured optical fiber. The result is a smooth spectral continuum. There is no consensus on how much broadening constitutes a supercontinuum; however researchers have published work claiming as little as 60 nm of broadening as a supercontinuum. There is also no agreement on the spectral flatness required to define the bandwidth of the source, with authors using anything from 5 dB to 40 dB or more. In addition the term supercontinuum itself did not gain widespread acceptance until this century, with many authors using alternative phrases to describe their continua during the 1970s, 1980s and 1990s.
Coherent addition of lasers is a method of power scaling. It allows increasing the output power and brightness of single-transversal mode laser.
The Trident Laser was a high power, sub-petawatt class, solid-state laser facility located at Los Alamos National Laboratory, in Los Alamos, New Mexico, originally built in the late 1980s for Inertial confinement fusion (ICF) research by KMS Fusion, founded by Kip Siegel, in Ann Arbor, Michigan, it was later moved to Los Alamos in the early 1990s to be used in ICF and materials research. The Trident Laser has been decommissioned, with final experiments in 2017, and is now in storage at the University of Texas at Austin.
Donna Theo Strickland is a Canadian optical physicist and pioneer in the field of pulsed lasers. She was awarded the Nobel Prize in Physics in 2018, together with Gérard Mourou, for the practical implementation of chirped pulse amplification. She is a professor at the University of Waterloo in Ontario, Canada.
The laser damage threshold (LDT) or laser induced damage threshold (LIDT) is the limit at which an optic or material will be damaged by a laser given the fluence (energy per area), intensity (power per area), and wavelength. LDT values are relevant to both transmissive and reflective optical elements and in applications where the laser induced modification or destruction of a material is the intended outcome.
János Hebling is a Hungarian physicist, known for his preliminary works at Terahertz physics and spectroscopy. He was born at Zirc on 9 May 1954 and currently works as a professor at the Institute of Physics at University of Pécs and is an active researcher at the Hungarian Academy of Sciences and ELI.
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